Fresh shooting has strained nerves in the Haitian capital, Port-au-Prince, where supporters of the ousted president were demanding his return.
Haitian police carried out joint patrols with the UN
Gunfire erupted when police entered the slum of Bel-Air, scene of a small rally in support of Jean-Bertrand Aristide.
But UN troops appear to have largely kept Aristide supporters from moving out of their strongholds through roadblocks and helicopter patrols.
Violence since the end of September has claimed at least 40 lives.
The centre of Port-au-Prince was largely deserted on Friday as businesses shut down in a protest against "terrorism".
Details of the shooting from inside Bel-Air were not immediately clear.
Haitian Justice Minister Bernard Gousse warned that his police force was not afraid to act against militants.
"The police will now put all their forces out on the street to make sure that those terrorists who are preventing people from going around their business and children
from going to school get what they deserve," he told a local radio station, Metropole.
In Bel-Air, 27-year-old resident Rosny Jean-Francois told Reuters news agency that the government was out to "kill or arrest anybody who supports Aristide".
UN helicopters flew over the city and troops in armoured vehicles patrolled key streets.
Brazil is calling for more UN troops to be sent to keep order
Mr Aristide's supporters had called for demonstrations to mark the 10th anniversary of his return from his first period in exile on 15 October, 1994.
He is now in South Africa, after fleeing a popular uprising earlier this year, but insists he is still the country's legitimate leader.
Haiti's interim government blames Mr Aristide's supporters for the recent surge in violence.
The UN peacekeeping mission is struggling to keep order, with just 2,600 soldiers - a fraction of the 6,700 troops and 1,600 police authorised for Haiti by the UN Security Council in the wake of Mr Aristide's departure.
Haiti's plight was worsened by last month's hurricane that wrought widespread devastation.
Brazil, whose troops form part of the multinational mission, on Thursday issued an urgent call for the UN force to be strengthened, warning of worsening violence.
The US has urged its citizens to leave Haiti and closed its embassy for the day on Friday.